Reflector antennas, including a parabolic antenna, are used in applications such as radio astronomy and satellite communication. Typical types of reflector antennas include multi-reflector antennas. The multi-reflector antenna includes a main-reflector having a central hole, a sub-reflector arranged at the front side of the main-reflector and opposing the hole, and a primary radiator or a beam delivery system arranged at the backside of the main-reflector. The multi-reflector antenna has advantages such as an ability to be used in common for multiple frequencies, and an ability to lower losses by shortening length of the waveguide connected to the receiver-transmitter.
Patent Literature 1 describes multi-reflector antenna device including a main-reflector, a sub-reflector, M (M≥1) focusing reflectors, and a primary radiator. This multi-reflector antenna device includes the sub-reflector and the focusing reflectors between the main-reflector and the primary radiator, to form a wave path for radio waves between the main-reflector and the primary radiator.